Farid M.F.A., Khamis H.S., Abou El-Nasr H.M., Ahmed M.H., Shawket S.M.

Transcription

1 Diet selection and food intake capacity of stall-fed sheep, goats and camels in relation to some physical properties of foods and their potential digestion in the rumen Farid M.F.A., Khamis H.S., Abou El-Nasr H.M., Ahmed M.H., Shawket S.M. in Lindberg J.E. (ed.), Gonda H.L. (ed.), Ledin I. (ed.). Recent advances in small ruminant nutrition Zaragoza : CIHEAM Options Méditerranéennes : Série A. Séminaires Méditerranéens; n pages Article available on line / Article disponible en ligne à l adresse : To cite this article / Pour citer cet article Farid M.F.A., Khamis H.S., Abou El-Nasr H.M., Ahmed M.H., Shawket S.M. Diet selection and food intake capacity of stall-fed sheep, goats and camels in relation to some physical properties of foods and their potential digestion in the rumen. In : Lindberg J.E. (ed.), Gonda H.L. (ed.), Ledin I. (ed.). Recent advances in small ruminant nutrition. Zaragoza : CIHEAM, p (Options Méditerranéennes : Série A. Séminaires Méditerranéens; n. 34)

2 Diet selection and food intake capacity of stall-fed sheep, goats and camels in relation to some physical properties of foods and their potential digestion in the rumen M.F.A. Farid, H.S. Khamis, H.M. Abou El-Nasr, M.H. Ahmed and S.M. Shawket Desert Research Centre, Al-Matareya, Cairo, Egypt SUMMARY - Four female camels, sheep and goats were individually fed ad libitum, barley grains, a commercial concentratemixtureandeithercloverhayorricestrawinseparate'feeders.dietselectionandfoodintake capacity were recorded. Dry packed volume, a suspension volume index, crude fibre content and indigestible crude fibre content remaining after 24 h in situ digestion of the foodstuffs were studied in a parallel laboratory experiment. Sheep consumed more barley grains than concentrate mixture whereas camels showed an opposite trend. Goats were practically similar to sheep, but they consumed the largest proportion of the roughage as compared to the other two species. Intake capacity per unit metabolic size was greater in sheep than in camels andgoats.acrossspecies,voluntaryfoodintakewasinverselyrelated to crudefibreintheselecteddiets. However, all selected diets had similar packed volume values and suspension volume indices indicating the relationship between the fill properties of foods and the intake capacity of ruminant animals which is apparently valid across species. Key words: Camels, goats, sheep, diet selection, food intake. RESUME - "Sélectiondurégimeetcapacitéd'ingestionalimentairechezdesovins,caprinsetchameaux alimentésenstabulationindividuelle,enrapportaveccertainespropriétésphysiquesdesalimentsetleur digestion potentielle dans le rumen'! Quatre chamelles, brebis et chèvres ont été alimentées ad libitum individuellement dans des nourrisseurs séparés avec du grain d'orge, un mélange de concentré commercial et, ou bien du foin de trèfle ou de la paille de riz. La sélection du régime et la capacité d'ingestion alimentaire ont été enregistrées. On a étudié dans une expérience parallèle en laboratoire le volume sec compacté, un index du volume en suspension, la teneur en fibre brute et la teneur en fibre brute indigestible qui restaient après 24 h de digestion in situ des aliments. Les brebis ont consommé plus de grains d'orge que de mélange de concentré tandis que les chamelles ont montré une tendance opposée. Les chèvres ont été semblables aux brebis, mais elles ont consommé la plus grande proportion de fourrages grossiers comparées aux deux autres espèces. La capacité d'ingestion par unité de taille métabolique a été plus grande chez les brebis que chez les chamelles et les chèvres. Au sein des espèces, l'ingestion alimentaire volontaire était inversement corrélée à la fibre brute danslesrégimessélectionnés.cependant,touslesrégimessélectionnésavaientdesvaleursdevolumes compactés et des indices du volume en suspension semblables, comme indicateurs du rapport entre les propriétés d'encombrement des aliments et la capacité d'ingestion des ruminants, ce qui semble apparemment valable pour toutes les espèces. : Chameaux, caprins, ovins, sélection du régime, ingestion alimentaire. Introduction In nutrition experiments on camels the requirements of cattle in similar physiological states were invariably used. The requirements recommended by Wilson (1984) were also patterned after those for European breeds of cattle. It was not until the recent publication of the camel's maintenance requirements for energy and protein (Farid et al., 1990; Farid, 1995) that feeding could be based on experimental findings. But maintenance is only one of the different physiological states of the animal and other states, e.g., growth, lactation and fattening, demand feeding at higher levels which require knowledge of the animal's feed intake capacity and its dietary preferences, both of which can be related to the physical, chemical and digestive properties of the feeds. The present communication reports findings from an experiment carried out to compare these faculties in dromedary camels, Barki sheep and local desert goats in an ad libitum cafeteria feeding experiment. 1 o9

3 Materials and methods Diet selection and voluntary food intake Four dromedary she-camels, Barki ewes and local desert does were used in two consecutive trials. All animals were non-pregnant and non-lactating adults and were housed individually in shaded floor pens. Each trial lasted four weeks with two weeks in between. The first week was for preconditioning of animals to cafeteria feeding conditions and the following two weeks represented an adaptation period. Data of diet selection, voluntary food and free water intakes were recorded during the fourth week. Body weights were recorded at the beginning and end of each trial. In the first trial animals were offered Egyptian clover (Trifolium alexandrinum) hay,a pelleted commercial concentrate mixture and cracked barley grains. In the second trial the hay was replaced with chopped rice straw. Foods were offered ad libitum and separated in divided feeders in order to allow for free selection by the animal and consequent recording of its intake from each foodstuff. Water was made available for one hour in the morning and daily free water intake was recorded. The proximate composition (AOAC, 1955) of the foods is presented in Table 1. Their nutritive values were calculated utilizing the equations of Kearl et al. (1 979) for sheep. Table 1. Average proximate composition and nutritive value (DM basis) and bulk indices of foodstuff s Foodstuffs Ash CP CF EE NFE DP ME ldcft PV SV1 (%) (%) (%O) (%) (%) (Mcal) (%) p/.) (ml/g) Rice straw O Clover hay Concentrate mix Barley grains t24 h indigestible crude fibre content measured in situ Physical and digestive properties of feeds Two indices of the physical properties were measured in a parallel laboratory experiment. The first was bulk density estimated by the graduated cylinder method of Montgomery and Baumgardt (1965) and expressed, as the packed volume (PV) of the air-dry material, ml The second, the suspension volume index (SW), was developed in our laboratory to measure the volume occupied by the food after hydration in aqueous suspension. This was measured by suspending exactly 25 g air-dry ground sample in 300 ml tap water in a 500 ml graduated cylinder at room temperature. The suspension was stirred by a glass rod for approximately one minute every 1 O minutes over a period of 90 minutes. The volume was then made up to the 500 ml mark with water, stirred once more taking care that no air bubbles were entrapped in the suspension and left to separate by gravity for 30 more minutes. The volume occupied by the suspended material, both the upper and lower phases, was recorded with the sum being the SV1 expressed in ml suspended volume per g air-dry feed (ml g-l). Twenty-four hours in situ rumen digestion of crude fibre was carried out using conventional dacron bag technique in two fistulated rams fed a mixed diet of Egyptian clover hay and a pelleted commercial concentrate mixture at slightly above maintenance. The contents were analysed for crude fibre using official procedures (AOAC, 1955). Measurements were carried out in duplicates in each animal to estimate the 24 h indigestible crude fibre content (241DCF%) of the feeds used in the in vivo experiment (Table 1). 110

4 Results and discussion Animal performance Relative weight changes are summarized in Table 2. Camels and sheep in the hay groups gained similarly, those in the straw groups gained less, a decrease of 23% in camels and 50% in sheep. Goats in the hay group did not perform as well and lost weight even though their intake was above maintenance requirements as indicated below, whereas those in the straw group deteriorated fast and that treatment had to be discontinued. Table 2. Voluntary food intake, diet selection and characteristics and free water intakei Sheep Camels Hay Straw Hay Straw Hay Live body weight (kg) Metabolic size Weight change (g d-l 100 kg"') O Dry matter intake day-') Total (g mix Concentrate grains Barley (%) l Roughage Daily intake (per l) 261 DM (9) ME DP (9) O Intake, multiples of maintenancett Energy (ME) Protein (DP) Characteristics of selected diets ME (Mcal kg-' DM) DP (g 100 kcal-' ME) CF (%DM) DCF (%DM) PV (ml g-' VI (ml g- ) Free water intake ml g*' DM m I ( tvalues are averages from four animals in each group ttenergy (kcal ME) and protein (g DP) maintenance requirements per Camels, 103 and 2.58 (Farid, 1995); Barki sheep, 108 and 2.68 (Farid et al., 1983) and goats, 111 and 2.69 (Kearl, 1982) Voluntary food intake and diet selection Voluntary food intake (VFI) was greater in sheep than camels whereas goats consumed the least. Also, animals in the straw groups consumed less total DM as compared to their mates in the hay groups (Table 2). On average, camels consumed 13.3% less DM than sheep, and straw feeding decreased VFI 9.5% in camels and 6.8% in sheep. Goats had the lowest total DM intake. However, these changes need to be considered along with changes in diet selection indicated below. Kearl (1982) reported average values of 70 and 68 g DM day-' for sheep and goats breeds of 111

5 developing countries, respectively. Maximum ad libitum intake values reported for dromedary camels in our previous experiments (Farid, 1995) choice intakes reported in the present experiment (Table 2). Diet selection, on the other hand, was radically different between camels and sheep. Camels consumed more of the higher protein concentrate mixture than from barley grains, whereas sheep showed an opposite trend in both hay and straw treatments (Table 2), except that it represented a greater proportion in straw fed animals, possibly to compensate for the lower nitrogen content of straw. The proportion of barley grains in total VFI was less in camels than sheep, and less in straw fed animals than in their hay fed mates. Hay comprised 13% of total VFI in both camels and sheep. When offered straw, camels nearly maintained its roughage proportion in total VFI, being 12.3%, whereas in sheep it decreased to only 4.8%. Goats represented a special case. Roughage percentage from hay was as high as one third of their ad libitum DM intake, possibly contributing to their lower total VFI because of physical limitation of the rumen. They resembled sheep in their diet selection, consuming less concentrate mixture than barley grains. Energy and protein intakes Energy and protein contents of the selected diets were calculated from values presented in Table 1. Intake per unit metabolic size and as multiples of the maintenance requirements of each species are presented in Table 2. Energy intake was less in camels than sheep, and was distinctly low in goats compared to both camels and sheep offered the hay roughage. Also, animals in the straw groups consumed less energy than their mates fed hay. Digestible protein (DP) intake, was slightly more in camels than in sheep, and was not apparently affected in the straw fed groups as those animals increased their consumption from the higher protein concentrate mixture. Goats had the lowest protein intake. Energy an8 protein intakes were compared to established requirements for the maintenance of live body weight of dromedary camels (Farid, 1995), Barki sheep (Farid et al,, 1983) and the goat breeds of developing countries (Kearl, 1982). Irrespective of roughage treatments and species, with the exception of goats, energy intake was about times their maintenance requirements. Protein intake was four times their maintenancerequirements, indicating possible preference for foods with higher protein content (Cropper et al., 1985, 1986). These intakes were conducive of the observed performance in terms of gain in weight as indicated above. Goats, although consumed 1.5 and 2.5 times their maintenance requirements of energy and protein they lost weight when fed the clover hay as roughage, and the experiment had to be terminated for the straw group. There is no simple explanation for this poor performance of goats under the present experimental conditions in comparison with either camels or sheep. Characteristics of selected diets The characteristics of diets selected free choice by the three species are summarized in Table 2. Energy density, Mcal Differences between camels and sheep and between hay and straw groups were negligible, being less than 4%. Although VFI was low and with larger proportion of roughage, the energy density of their selected diet was not practically different from the other two species. The protein-energy ratio was in favour of camels compared to sheep. Goats fed clover hay were intermediate.according to establishedmaintenancerequirements cited above, the protein-energy ratio. of maintenance diets was constant for the three species ranging between 2.4 and 2.5 g DP 1 O0 kcal ME, considerably lower than the observed values at free choice ad libitum intake. 112

6 It was of interest to examine differences in the content of crude fibre (CF%) and 24 h indigestible crude fibre (241DCF%) of diets selected by the three species. Also the differences in the physical properties of the selected diets, indicative of;.rumen fill, namely the packed volume (PV) and the suspension volume index (SVI), both in ml g- (Table 2). In all cases, the free choice selected diets were low in crude fibre. In goats offered clover hay it was somewhat greater than in the other two species. Only goats nearly approached the recommended minimum level of dietary CF content for the properfunctioning of therumen,beingapproximately ondrymatterbasis. The 241DCF content of the selected diets followed the same pattern as the CF content. The volume indices of the selected diets were practically constant in camels and sheep (SV1 range: ml g?') and about 20% greater in goats (5.7 ml g- ). The dry packed volume (PV) followed a similar trend (Table 2). The relationships between fibre contents and volume indices of the selected diets and the voluntary food intake of the animals can be observed from data presented in Table 2. The general trend was that VFI decreased as the CF% and 241DCF% increased. On the other hand, PV and 'SV1 of the selected diets were remarkably constant irrespective of the animal species or the type of roughage offered. These findings are in general agreement with the classical reports on the physical-physiological regulation of voluntary food intake in ruminant animals (Conrad et al., 1964; Montgomery and Baumgardt, 1965; Farid and Hassan, 1976; Forbes, 1995). Free intake l l Free water intake, ml g-' DMI, was not practically different between the three species when fed the clover hay but increased when fed straw. When expressed per unit body mass, ml it was 41.4 and 18.3% greater in sheep than camels when fed hay and straw, respectively. Goats were similartocamels.strawfeeding increased it in camelsonly by 19.8%. The reportedvaluesare possibly minimal and not reflecting the true differences between species in their natural environment since the animals were. housed indoors. l References AOAC (1955). OfficialMethods of Analysis. gthed.association of OfficialAgriculturalChemists, Washington, DC, p Conrad, H.R., Pratt, A.D. and Hibbs, J.W. (1964). Regulation of feed intake in dairy cows. Changes in importance of physical and physiological factors with increasing digestibility. J. Dairy Sci., 47: Cropper, M., Lloyd, M. andemmans,g.c. (1985).An-investigationinto the relationshipbetween nutrient requirements and diet selection in growing lambs. Anim. Prod,, 40: 562. Cropper, M., Lloyd, M., Emmans, G.C. and Hinks, C.E. (1986). Choice feeding as a method of determining lamb nutrient requirements and growth potential. Anim. Prod., 42: Farid, M.F.A. (1995). Nutrient requirements of dromedary camels: protein and energy requirements for maintenance. J. Arid Environ., 30: Farid, M.F.A. and Hassan, N.I. (1976). The supplementary feeding of growing sheep under simulated drought conditions. Alexandria J. Agr. 24:' Farid, M.F.A., El-Shennawi, M.M., Mehrez, A.Z. and Salem, A.M.M. (1983). Protein requirements for maintenance of Barki desert sheep. World Review Aním. Prod., 19: Farid, M.F.A., Shawket, S.M. and Abou El-Nasr, H.M. (1990). The maintenance requirements camels: a preliminary evaluation. Alexandria J. Agr. 35: of Forbes, J.M. (1995). Voluntary Food lntake and Diet Selection in Farm Animals. CAB International, Oxon, UK, p

7 Kearl, L.C. (1982). Nutrient Requirements of Ruminants in Developing Countries. Feedstuffs Institute, Utah State University, Logan, p International Kearl, L.C., Harris, L.E., Lloyd, H., Farid, M.F.A. and Wardeh, M.F. (1979). Arab and Middle East Tables of Feed Composition. Damascus: The Arab Centre for The Studies of Arid Zones and Dry Lands, The league of Arab States, p Montgomery, M.J. and Baumgardt, B.R. (1965). Regulation of food intake in ruminants. 2. Rations varying in energy concentration and physical form. J. Dairy Sci., 48: Wilson, R.T. (1984). The Camel. Longman, London, p